Method of manufacturing an expansion element

ABSTRACT

Expansion element consisting of a corrugated stainless steel pipe welded to stubs of normal steel, the said weld being made by depositing stainless steel as a welding material onto end surfaces of the stubs, milling the deposited material for forming a substantially radial and a substantially cylindrical surface intersecting each other and welding the corrugated pipe to said surface.

ite it it [191 Eeinper [54] METHUD @E MANUEACTUEHNG AN EXEANSHUN ELEMENT[76] Inventor: Johannes A. ifiemper, c/o N. V.

Machinefabrie Arnhem, Industriestraat 9, Arnhem, Netherlands 22 Filed:May12,1971

21 Appl. No.: 142,735

[30] Foreign Application Priority Data May 12, 1970 Netherlands..7006873 [52] US. Cl ..29/47l.i, 29/482 [51] int. Ci. .E23k 31/02 [58]Field oil Search ..29/471.1, 475, 482, 29/483, 500, 501, 502

[56] References Cited UNITED STATES PATENTS 2,787,699 4/l957 Jessen..29/47l.1 X

[111 3,73%,Efi3

[ 1 May 22,1973

3,248,134 4/1966 Pennington ..29/47l.l X

3,286,341 11/1966 Miller ..29/47l.l 3,525,144 8/1970 Katunich et a1...29/47l.l

Primary Examiner.l. Spencer Overholser Assistant Examiner-RichardBernard Lazarus Attorney-Paul & Paul [57] ABSTRACT 3 Claims, 4 DrawingFigures PATENTEU MAY 2 2 I975 JOHANNES A- KEIVI PER METHOD OFMANUFACTURING AN EXPANSION ELEMENT The invention relates to an expansionelement, provided with a corrugated pipe of thin stainless steel, whichhas on both sides been connected with a pipe stub of steel. According toa known process the attachment of such corrugated pipes to the pipe stubtakes place by means of brazing. In practice it has been proven, thatowing to this, relatively substantial leakage has occurred. The brazedjoint was namely not always reliable and could show leakage. A furthercause of leakage was, that during the welding of the pipe stubs to otherpieces of pipes the temperature of the brazed joint sometimes became sohigh, that the joint became weak or separation occurred thereat.

According to a further known process at first a con nection portion ofstainless steel is welded to the pipe stubs, and then the ends of thecorrugated pipe are welded to the said connection portion. With thisknown process it may happen that the end of the thin corrugated pipe isburned down. Moreover in the practice of this known process it isnecessary to mount the welded stainless steel in such a way thattensions due to shrinking caused by the difference in the thermalcoefficient of expansion between steel and stainless steel remainlimited and are transmitted to the corrugated pipe as little aspossible.

The invention aims at solving said difficulties in a simple way.

Accordingly it is provided according to the invention that portions ofstainless steel are welded on the surfaces at ends of the pipe stubs,that said portions subse quently are partly milled or removed in such away that two axially symmetric surfaces intersecting each other areobtained and that the ends of the corrugated pipe are put in abuttingrelation to said surfaces and are welded to them.

It has appeared that in this way a reliable connection between the endsof the corrugated pipe and the pipe stubs can be effected and reliableresults can be obtained with the available welding techniques, such asthe so-called micro plasma welding or even with argon arc welding.

In practicing this invention it is possible to make further welds nearthe connection between the corrugated pipe and the pipe stubs. Thispossibility is made use of according to a further elaboration of theinvention by welding a protecting sleeve to the one pipe stub, saidsleeve being capable of sliding along a sleeve welded to the other stub.

Said sleeves which are permanently connected with the pipe stubs notonly serve as protection for the expansion element but also serve as astroke or displacement limitation of the expansionelement becauseaccording to a further elaboration of the invention one of the sleevesis provided with one or more abutment members, protruding intoone ormore longitudinal recesses of the other sleeve.

The said axial symmetric surfaces may form a ringshaped plane surfaceperpendicular to the axis of the pipe stub and a cilindrical surfaceforming a thin tubular coaxial extension of the pipe stub.

Preferably a flange is formed at the end of the corrugated pipe, saidflange being put against the outer plane of the said radial ring whichhas been welded to the pipe stub, so that the thin tubular extensionfits closely in the end of the corrugated pipe, after which the radialring and flange and the tubular extension and the end of the corrugatedpipe are both welded together. Said latter welding joint preferablytakes place without supplying material for the welding.

According to a further improvement of the invention it is provided thatbetween the protecting sleeve and the corrugated pipe a spacer ordistance ring is mounted, which ring preferably consists of a pluralityof ring sectors, e.g. two ring sectors.

In the following the invention is further elucidated with reference tothe accompanying drawing, in which:

FIG. 1 shows halfa section through an expansion element according to theinvention; and

FIGS. 2, 3 and 4 elucidate successive stages of the welding.

In the drawing by l a corrugated pipe of stainless steel has beenindicated. The material of such a corrugated pipe generally isrelatively thin, e.g. 0.3 mm. Owing to this it is, however, extremelydifficult to weld this material to normal steel. The corrugated pipe hasa number of protrusions and recesses, by which extension and shorteningis possible with relatively small re action forces. A pipe stub 2 iswelded to the left side of the corrugated pipe, to which stub aprotecting sleeve 3 is welded, comprising a long cylindrical portion anda shorter conical portion 4. The protecting sleeve 3 is, just like thepipe stub 2 of construction steel. In the protecting sleeve a pin 5 hasbeen mounted. A pipe stub 6 has been welded to the right side of thecorrugated pipe 1 to which stub 6 a sleeve 7 has been attached with aconical portion 8, said sleeve having a slot-shaped recess 9, in whichpin 5 fits. Furthermore, a distance ring 10 has been mounted between thesleeve 3 and the corrugated pipe, said ring being preferably divided foran easy mounting and preferably consisting of two half rings. Saiddistance ring prevents the corrugated pipe from collapsing, which easilycan take place when pipe stubs 2 and 6 after being welded to a pipingsystem have not completely been aligned. Such a collapse leads tofriction against sleeve 3 when the corrugated pipe expands and shrinks.This easily leads, as experience has shown, to leakage of the corrugatedpipe.

In FIGS. 2, 3 and 4 a preferred embodiment for making the weld between apipe stub, such as 2 and the corrugated pipe 1 has been furtherelucidated. First a quantity of stainless steel is welded to the endsurface 11 of pipe stub 2, as shown in FIG. 2. Said quantity ofstainless steel substantially has the shape of a ring 12. Part of saidring is subsequently milled off, in such a way, that a thin radial ring13 and a tubular portion protruding in the axial direction of stub 2remain.

In FIG. 4 the same has been indicated on an enlarged scale. At the endof the corrugated pipe 1 a flange 15 has been formed. By shiftingportion 1 in FIG. 4 with the flange 15 to the left until the flangeabuts the plane 13 and the innerside of corrugated pipe 1 fits over theouter side of the tubular protrusion 14 and then joining the wholeconstruction e.g. by means of micro plasma welding, without materialsupply, a weld is being formed.

It has appeared that in this way a very reliable welding connection isobtained.

What I claim is:

l. A method for making an extension element by welding the ends of athin corrugated pipe of stainless steel to pipe stubs of steel,comprising the steps of placing a deposit of stainless steel on an endplane of each of the pipe stubs of steel, then milling off part of eachdeposit in such a way that two axial symmetric surfaces intersectingeach other are obtained in each deposit, then placing the ends of thethin corrugated pipe of stainless steel in fitting relation to one ofsaid surfaces and abutting relation to the other of said surfaces ofeach of the pipe stubs, and then welding the corrugated pipe to saiddeposits on said pipe stubs.

2. The method of claim 1, characterized in that, with respect to eachpipe stub, both the surfaces obtained by the milling off are mutuallyperpendicular; the one surface being a cylindrical surface coaxial withthe pipe stub and the other surface being a radial surface,perpendicular to the axis of the pipe stub.

3. The method of claim 1, characterized in that at least one end of thecorrugated pipe, before being welded to a deposit associated therewithis provided with a radial flange.

1. A method for making an extension element by welding the ends of athin corrugated pipe of stainless steel to pipe stubs of steel,comprising the steps of placing a deposit of stainless steel on an endplane of each of the pipe stubs of steel, then milling off part of eachdeposit in such a way that two axial symmetric surfaces intersectingeach other are obtained in each deposit, then placing the ends of thethin corrugated pipe of stainless steel In fitting relation to one ofsaid surfaces and abutting relation to the other of said surfaces ofeach of the pipe stubs, and then welding the corrugated pipe to saiddeposits on said pipe stubs.
 2. The method of claim 1, characterized inthat, with respect to each pipe stub, both the surfaces obtained by themilling off are mutually perpendicular; the one surface being acylindrical surface coaxial with the pipe stub and the other surfacebeing a radial surface, perpendicular to the axis of the pipe stub. 3.The method of claim 1, characterized in that at least one end of thecorrugated pipe, before being welded to a deposit associated therewithis provided with a radial flange.